User-Centric Blind Interference Alignment Design for Visible Light Communications

Visible light communications (VLC) are considered as a key technology for future wireless communications. In order to mitigate the interference, several transmit precoding (TPC) schemes have been proposed for VLC. However, beyond the need for channel state information and backhaul links, the TPC schemes are subject to additional constraints given by the features of the optical channel such as ensuring a real and non-negative transmitted signal or a low correlation among users. Besides, the traditional network-centric (NC) design, i.e., considering only the position of the transmitters, leads to rigid transmission schemes for VLC networks due to the small and confined coverage of the optical transmitters.In this paper, we consider blind interference alignment (BIA) schemes for VLC, which solve the aforementioned issues, based on the concept of reconfigurable photodetector. In this context, we propose a user-centric (UC) clustering strategy based on the K-means algorithm where the users are treated as an active element of the network instead of a mere endpoint. For the proposed UC design, we derive two BIA schemes based on the connectivity of the clusters; a straightforward scheme considering each cluster as a broadcast channel referred to as KM-sBIA and a scheme that is flexible to the connectivity of each user within the cluster referred to as KM-topBIA. The simulation results show that the proposed schemes outperform the use of classical TPC or other BIA-based schemes considering both NC and UC approach.